/Engine/Source/Runtime/SlateCore/Public/Widgets/SWindow.h
Animate the window to TargetOpacity and TargetShape over a short period of time
void MorphToShape ( const [FCurveSequence](API\Runtime\SlateCore\Animation\FCurveSequence) & Sequence, const float TargetOpacity, const [FSlateRect](API\Runtime\SlateCore\Layout\FSlateRect) & TargetShape )